Metallic nanoparticles are useful for a wide-variety of applications and have generated a great deal of scientific interest, because they effectively a bridge between bulk materials and atomic or molecular structures. Standard metallic nanoparticle synthetic approaches exploit controlled reduction from a homogenous reagent solution; control over reaction conditions yields excellent uniformity of particle size and shape. (See, e.g., C. B. Murray, et al., Annu. Rev. Mater. Sci. 30, 545 (2000); J. Hu, et al., Acc. Chem. Res. 32, 435 (1999); Y. N. Xia, Adv. Mater. 15, 353 (2003); Y. Liu and A. R. H. Walker, Angew. Chem., Int. Ed. 49, 6781 (2010); T. Yu, et al., Angew. Chem., Int. Ed. 50, 2773 (2011); R. Jin et al., Science 294, 1901 (2001); A. C. Templeton, et al., Acc. Chem. Res. 33, 27 (2000); A. M. Jackson, et al., Nat. Mater. 3, 330 (2004); D. V. Leff, et al., Langmuir 12, 4723 (1996); M. C. Daniel and D. Astruc, Chem. Rev. 104, 293 (2004); and S. A. Claridge et al., ACS Nano 3, 244 (2009), the disclosures of each of which are incorporated herein by reference.) However, alloy nanoparticle synthesis is considerably more challenging. Synthetic approaches include co-reduction and organometallic chemistry; particles are generally bimetallic, many elements are incompatible, and there are limitations of composition range and product uniformity. (See, e.g., W. Chen, et al., Langmuir 23, 11303 (2007); and B. N. Wanjala et al., Chem. Mater. 22, 4282 (2010), the disclosures of which are incorporated herein by reference.)